Air brake



Oct. 28, 1941. L. A. SAFFORD 2,260,485

AIR BRAKE Filed Feb. 24, 1941 x lhwentor 01m: QL. b a H 0 25 (sn g.

attorncgs Patented Oct. 28, 1941 Lewis A. Safford, Watertown, N. 'Yl, 'alssignor'to The New York Air' BrakeC'ompany, a corpora-'1 tion of New Jersey Application February24, 194i, Serial Nb. 330,345

1' Claim. I

This invention relates to air brakes and particularly to flow controlling chokes and arrangements protecting such chokes from water. This is important because in winter the freezing of water in the choke may seriously derange the valve and cause erratic operation. v i

The invention is capable of usein many cases where a metering choke is used in conjunction with a by-pass or other flow port, but the invention has particular utility in connection with an emergency vent valve constructed by applicantsassignee under Patent 2,069,914, issued to said assignee upon an invention of Charles A. Campbell on February 9, 1937.

In the Campbell patent aforesaid the piston pins which function to unseat 'the vent valve through which the brake pipe is vented to. atmosphere in response to emergency reduction of brake pipe pressure. The piston is interposed between a chamber subject to brake pipe presfrom the brake pipe to the quick action chamher, but also affords back flow from the quick action chamber to the brake pipe to prevent response of the piston during service reductions of brake pipe pressure. 4 I

This second port is closed by'extreme motion of the piston toward the quick action chamber against spring resistance. I restricted charging at the head of the train during brake releases and a more rapid breathing rate in both directions between the brake pipe and the quick action chamber at all times. In the Campbell patent above identified the choke is mounted in the upper face of the piston and hence is quite exposed. The by-pass port is drilled radially through the rim "of the piston and is exposed to water reaching the piston, if this accumulates in any considerable quantity.

According to the present invention the general flow control is substantially the same as that disclosed in the Campbell patent but the choke is located in the cylinder bushing at a 1 I point below the lowest position reached by the packing ring of the piston so that the choke is always protected by the piston. The flow pasmoves in a vertical direction and has guiding The effect is to give 3 likely tobe reached by water,.through a drilled passage. partly in .the vent' valve housing and partly in the bushing, toLa clearance groove cut in the'inner iace'of the. bushing below the lowest position reached by the packing ring .of the piston. In t his way, both ,the choke land the flow 3 33 Particularly Wellprotected against the entranceof water.

In the prior, Canipbell device the choke and thenormal charging passage are always in parallel, whereasin the present device flow to the choke is through the Joy-pass passage. f The ultimate effects are the sameexcept that the choke isin a position in which it issafe from water. In the embodiment illustrated the entrance to the Char i g pathisabove anywater level ever reached in the normal operation of the device, and obviously canbe made as high as seems de- 'sirable, within the limits imposed by the form offthe valve housing. H

Exceptior the location of the charging flow passages, the construction of the vent valve is essentially the same as that shown in the Camption can be" adequate y explained by reference to ,aj' e i yew lwh q in. t accompanying drawing, isa vertical axial section through the complete 'ventf'valve. It should, be understood 9 that the arrangement of the guide pins hereafter inentionedi islthat illustrated in Fig. .3 of the prior Catmbbllfpflehtfbiit since thatarrangeis not a feature of the present invention itneed' -not be discussed in] detail.

" Referring now to thegdrawing, the body of the vent valve'comprises a'housing'fi with a brake pipe connection I! having a bolting flange 3 and a screens "A removable cap ll closes an opening in the top of housing ,6. Bolted to housing '6 is a cup-like shell l2 ,Whichengcloses the bal- 'ancing chamber l3. Such a balancing chamher is sometimes calledinthe art a quick act o mbe -i i Clampedfbetween, the body 6 and shell l2 and 's'ealedby a gasket i9" is the cylinder bushing l4 which is formed atfits, lower margin with the :se'aling' 'rim l5 and which carries a pendant yoke 16. The yoke l6 carries the hub, l'l which guides the stem [8 of the emergency piston IS. The piston l9 works minebushing l4 and has a metallic packing ring 2i (sometimes called a snap ring). The piston l9 .also c arrieson .its lower face a'gasket 22 of rubber-like material. The gasket 22 is arranged to seal on the rim l5 when sage leads from a point above the highest level the piston is in its lowermost position.

A cup 23 is threaded on the lower end of the hub l1 and guides a shiftable stop 24 which is urged upward by a coil compression spring 25. The lower end of the spring 25 is sustained by the cup 23 and the spring urges the stop 24 upward against the lower face of the hub IT. The parts are so dimensioned and arranged that when the stop'is 'in its uppermost'position just defined it'so positions the lower end of stem l8 and the connected piston l9 that the gasket 22 is spaced slightly above the rim l5. This'is the position shown in the drawing. However, if the ,V .e rise of brake pipe pressure be sufiiciently rapid,"

the piston will be forced down againstjthe re-,

sistance of spring 25 until the gasket 22wiseals tightly against the rim [5.

In the housing 6 an upstanding annular valve seat 26 on which the main ventvgiv i 21: seats. The valve 21 has a central port-sur-- rounded by asmallerseat 28: and on this avpilot valve 29 seats} "A fcoilLcompression "spring 31, seated withinl'a upf3 2,which'.-is carriediby the cap I I, reacts do 'Qfwardjon' the valve 29 and consequently serves to urg' both" valves 'closed. -IAn atmospheric; government); {at 33 leads from the 'space'withinlthe 'seat 26. ,The piston .119 car ries three upstandin'g'guide pins- 34, only'twoof which are visible in the drawing, the thirdone being forwardofthe plane ofsectiom They are A uniformly spaced around the axis of the piston, thearrangement conforming-to thatshown in Fig.- 3' ofthe Campbell patent. v

Theipins 34 Tpasskthrough wings- 35 and 36 shown in the drawing. Charging flow to the quick action chamber [3 from the brake pipe then takes place through the passage 44, and thence between the gasket 22 and rim l5. At such times the flow through the choke 46 is inconsequential.

If brake pipe pressure rises more rapidly, as it commonly'does during brake releases on the leading twenty cars or so of the train, the piston I9 will overpower the spring 25 and the gasket 22 lwill seal on the rim l5. At such time charging flow is limited to the capacity of the choke 46. The effect is to proect the quick action chamber against overcharge at times when the pressure differentialacting downward, on piston I9 is excessi ve When the differential diminishes, the

piston will resume the normal position shown in the drawing and'charging will then occur at a more rapid rate, determined by the capacity of which respectively are, formed integrally-with the valves v2! and .291 The pinsare shouldered as indicated at 31.- and 38,;the spacing being such that when the pistonrises from. the position shown in the; drawing it first moves idly for-a short distance, then' engages-{and unseats the valve 29, and on further upward-motion faciliifltd y the opening of thevalv'e 29 unseats the valve 21. v 1 c t The mechan'sm so describe d will be recognized as confo-rming;to.the disclosure of the prior Campbell patent.= "There is an additionalillustrated detail not involved in the present inven- .tion comprising abore inthe-stem l8 which is closed at its uppere'nd-by a plug, and which This delivers'oil =-through the :ports generally indicated-"at 43- to i the guideway in the hub 1 '1.

Charging flow and-[back flow to and-from the quick action chamber, I3 is provided for by means of'the passage 4 4'which comprises communicat- ,ing drilledpassages-inbody 6 andbushing [4.

This leads from-the opening in which-one pin 34.. works, to -a groove 45 cut in the inner face ofbushing -l4-above rim -l5 and below the lowest traverse of ringll: -Withingroove- 45-and leading through bushingflis a choke port -46 of limited capacity; This choke port 46 affords-slow charging fiow through the bushing, when-gasket '22 seals on rim l5. All three pins;34-extend upward through passages whose upper ends'are well above the bottom -of housing 6, so thatthe passages are well protected against theentrance .of water from the brake pipe. Very slight rotary motion of the piston is possible.-

I .I rq i In. charging the 'system' at normal ratesrof brakepipe riselthe parts assume the position encloses an oil saturatedlabsorbent mass 42.

upper side ot piston, l9, which inherently results;

from the openinglof valvef'25, thepistonwill 'im mediately move upward full stroke and so uni seat also the valve/fluff,- 4 '7 The elevated entran'ce' to' pasasge 44 and, the. locationof the chokejpjort 46' so that it is always below the piston '21 afford remarkably v complete protectio'n'jto thef'i choke against water which sometimes enters the'housingflfi from, the brake I pipe. i. ,M Variations. of F detail arepossible within the spope of the invention, While the. entrancelto the upper. end of passage 44v asv shown is high;

enough for all,pract'ical purposes, it obviously canbe made even. higher bylmere change, of design;.'. q

Means for controlling charging and breathing flows between a brake pipe in which'functional pressure changes occur at difierent-rates andin reverse-directions, and areservoir charged therefrom, comprising a cylinder havinga sealing rim; a piston vsubject on its opposite sides to brakepipe. and reservoir pressures and movable toward said rim, by preponderating brake pipe pressure, said piston having its periphery in-sealing-engagement with said cylinder and having on the reservoir side thereof means for forming withsaid cylinder rim'a second seal which-is spaced fromsaid peripheral seal, the cylinder and piston being formed toafford a clearance between said seals; means'forming a normal flow path of limited capacity connecting'said clear- ,ance, with. the brake pipe, such connection communicating with the brake pipe at apointr-above the highest level reached by the pistong'means forming a flow path of more limited-capacity than said normal flow path between said clear- .ance space and the reservoir; and a yielding stop serving,-except when its resistance isiovercome, to -hold-said piston'spaced from said rim. 1 LEWIS A. SA'FFORD.- 

